Scientists tell us that brain development in the early years is guided by experience. We arrive in this world with too many neurons and too few connections. Then our experience, it seems, dictates which neurons we keep (and which we discard) and what connectors we grow. It is like building roads. We need highways between places we visit often, smaller roads to places we visit less often. When we rarely, if ever, need to communicate between this neuron and that one, there is merely a footpath and with no use, it disappears. That is what is happening in the young brain. Brain roads are being built and the map depends on what the baby does and does again and does yet again.

So if we have a baby who for a variety of reasons cannot or does not explore the world of people and the world of objects, that baby will not be reinforcing, and thus keeping, the same neurons as a typically developing child and will not be growing the same connectors or synapses. This baby, the atypical baby, may have such limited abilities for experience that different and maybe fewer neurons are kept and are reinforced repeatedly due to the baby's limitations, until there are not many roads in the brain but just a few.

What normally guides the baby in the process of exploring the world of people and objects? What gives the baby pointers towards the wonderful range of valuable experiences that will help the brain develop fully and functionally? One of the answers is joint attention. Joint attention is the ability to share experience with another person, to look at things together, to share wonder, laughter, even concern. This is a very early skill and it seems that babies are hard wired to do this -- to share experience and to jointly attend to world events.

Butterworth and Jarrett, in 1991, did a wonderful study about this drive of ours to share experiences with others. The researchers set up eye gaze studies with 6-month-olds, 1-year-olds and 18-month-olds. The babies were placed in a highchair facing their mothers and the mothers were told to look at various things while the researchers looked for the baby's reaction. At 6 months of age, babies would look to the side, following their mother's gaze if that gaze involved an obvious turn of the head. At 12 months, babies would follow the mother's gaze if she simply used her eyes to look to the side. At 18 months, the babies would follow the mother's gaze to a spot on the wall behind the baby's head by twisting in their highchairs to see what their mother was looking at behind them. What seems to be a strong message from this study is that babies, from very early on, are driven to figure out what their mothers are experiencing. It is as if the babies are thinking: What are you looking at, Mom? What are you seeing? I want to see it too. Babies are highly motivated to share the experience of others and seem to have the capacity to do so from very early in development.

The ability to share experience through joint attention opens the door for another essential vehicle for learning - social referencing. Here the baby uses the adult's wisdom to help shape their experience. Show them something new, wondrous, and scary and they will check in with Mom or Dad: what do you think about this? The young child is a master at reading other people's facial expressions, at hearing and interpreting the tone of their voice, at understanding their body language. And not only do they read this communication; they use it to help them interpret what is going on.

Think of a new toy the baby sees, something spinning and shiny and maybe a little frightening… The baby sees it and then looks to Dad. Is this okay? Do you like it? The baby gets information from Dad that the toy is exciting and fun. The baby then begins to see the whirling item as wondrous and not as frightening. Through joint attention, Dad is not only sharing the experience of this ever changing and growing world with the baby, he is helping the baby establish meaning.

A classic example of this might be a scenario where a stranger comes to the door. The baby uses her senses to identify the person as a stranger. Her memory then tells her that she is scared of people she doesn't know. Then she looks at her grandmother who is welcoming the stranger with a big smile. By referencing her grandmother's affect, the baby is able to modify her own affect, attuning her emotional state to her grandmother's emotional state. She uses her perceptions (I see a stranger), her memory (I'm afraid of strangers) and the emotional information she gets from her grandmother to establish meaning. Sometimes the baby's own intense feelings will override the information she is getting from a trusted adult. And then attunement is not possible. But often the baby will use the perceptions of others to establish what an event means.

What is remarkable about all of this is not only that babies use people to help them establish meaning, but that this social referencing and affective attunement solidifies a very important development in the young brain. When babies shift their thinking to match the reactions of the guiding adults, they are demonstrating mental flexibility. This is the skill that lets us imagine things. For example, we can think about and picture our bedroom. And then, with little difficulty we can insert in this picture something new and different and never before seen in our bedroom. We can do this because we have mental flexibility. We are imagining things never experienced. And we do it all the time. Mental flexibility is the foundation of imagination and higher-level thought. It is a crucial step in the brain's development.

So how do babies learn all this? How do they learn to share experience and check in with others to get information about their experience? It begins with joint attention. Babies, counting on others to help them, use joint attention, social referencing and affective attunement to derive meaning about life's events. In the process, they develop the flexibility needed for many other kinds of thinking.

So back to the developing brain, those neurons and synapses… Babies' brains develop according to use and experience. They develop through exploration, an exploration that is guided and supported by sharing experiences with others who help interpret the meaning of these experiences. It is this involvement with others that helps the baby to grow and develop, and ultimately helps to shape the map of the brain.